The Interior Department has quietly rolled back an Obama-era policy aimed at protecting migratory birds, stating in a solicitor's opinion that it will no longer prosecute oil and gas, wind, and solar operators that accidentally kill birds.

The new interpretation of the Migratory Bird Treaty Act (MBTA), which was issued Friday, marks a win for energy interests that described the federal government's previous position as overreaching. On Jan. 10, before President Trump's inauguration, Interior had issued an opinion declaring that operators could face legal liability for the incidental deaths of birds ensnared by uncovered oil-waste pits or unmarked transmission lines. The law in question, enacted in 1918, makes it illegal to "pursue, hunt, take, [or] capture" migratory birds without a permit, and the dispute centers largely on how to interpret "take."

In the new opinion, Interior's principal deputy solicitor, Daniel Jorjani, wrote that applying the law "to incidental or accidental actions hangs the sword of Damocles over a host of otherwise lawful and productive actions, threatening up to six months in jail and a $15,000 fine for each and every bird injured or killed."

Before joining the Trump administration, Jorjani worked as general counsel for Freedom Partners Chamber of Commerce, a project of the billionaire oil executives Charles G. and David H. Koch.

David O'Neill, chief conservation officer for the National Audubon Society, said in an interview Tuesday that the policy reversal could make it less likely that energy operators would invest in precautionary measures to prevent bird deaths. He said that the prospect of legal liability had fostered efforts such as developing bird-friendly guidelines for placing transmission lines.

"We just don't want to lose any incentive for the industry to come to the table and work through this with us," O'Neill said. "And the solutions are out there."

Energy groups such as the National Ocean Industries Association (NOIA) and the American Petroleum Institute (API) hailed the new interpretation as a reasonable approach to a vexing problem.

"Over the last few years, the management of 'take' under MBTA has been riddled with flawed decisions that have created massive uncertainty," said Tim Charters, senior director of government affairs for NOIA. "This common-sense approach ensures that lawful activities are not held hostage to unnecessary threats of criminalization."

Collin O'Mara, president of the National Wildlife Federation, said in an interview Tuesday that the new opinion will not provide the kind of certainty both industry and conservationists have sought for years. While the Obama administration interpretation was too sweeping, O'Mara said, the new one is far too narrow.

"We're seeing the whipsaw from one extreme to the other," he said, adding that when it comes to Interior's energy policies, "one year in, there's been no balance. If the choice is between energy and conservation, energy always wins."

O'Mara said that a federal regulation outlining permitting standards would provide the kind of certainty needed for these energy projects. The Obama administration worked on crafting such a rule but failed to finish it.

The House Committee on Natural Resources recently adopted an amendment by Rep. Liz Cheney (R-Wyo.) as part of a broader energy bill that would abolish incidental take as a violation of the MBTA. A slew of energy interests are registered to lobby on the issue this year, according to federal records, including the Solar Energy Industries Association, Siemens, the National Stripper Well Association and the gas industry's GPA Midstream Association.

Over the years, the federal government has used the MBTA — which was enacted to stem the widespread slaughter of birds at the turn of the 20th century for millinery and other purposes — to impose large fines after environmental disasters. BP agreed to pay $100 million for violating the act as part of its compensation for the 2010 Deepwater Horizon spill; the money was earmarked for wildlife habitat restoration.

But Interior's deputy communications director, Russell Newell, said in an email that the fact that "the government has relied on prosecutorial discretion" has led to "tremendous uncertainty in how the act will be applied."

"Interior's action on the MBTA is a victory over the regulatory state," Newell said, adding, "There remain several other statutes, including the Endangered Species Act and the Bald and Golden Eagle Protection Act, that continue to provide protections to birds."

One of the sharpest critics of the MBTA is Harold Hamm, chief executive of the energy exploration company Continental Resources, who served as Trump's energy adviser during the 2016 campaign. In 2011, a U.S. attorney in North Dakota charged Hamm with a criminal misdemeanor after a Say's phoebe got stuck and died in a pond of oil waste. Hamm fought the charge and got it dismissed in 2012.

Trump attacked the Obama administration over the incident during an energy speech in May 2016.

However, Trump also has repeatedly criticized wind energy for causing bird deaths.

"The wind kills all your birds. All your birds, killed," Trump remarked during a rally in Pennsylvania in August 2016. "You know, the environmentalists never talk about that."

While exact estimates are difficult to find, hundreds of thousands of birds probably die each year when they become caught in wind turbine blades. Oil-waste pits kill between a half-million and 1 million birds each year, according to Audubon, while power lines cause the death of up to 175 million birds per year.

O'Neill said it's "ironic" that Trump has lamented how birds are dying from flying into turbines when "he's gutting one of the best tools we have to make sure the wind industry is properly siting these projects."